Vista Beta 1 and Longhorn Server Beta 1 include a new implementation of the TCP/IP protocol suite known as the Next Generation TCP/IP stack. The Next Generation TCP/IP stack in Windows Vista and Windows Server Longhorn is a complete redesign of TCP/IP functionality for both IPv4 and IPv6 that meets the connectivity and performance needs of today's varied networking environments and technologies. Elsewhere, will Office 12 be named... Office Mondo?

Maybe Microsoft wan'ts to get rid of open-source netstack which is part of the "viral software". Also they have now tool to make life of non-Microsoft systems difficult in Microsoft-only LANs that may require the next generation net stack for increased security etc. Probably Microsoft even dream of Windows-only Internet in distant future.